Ceramic matrix composites (“CMCs”) include fibers that are embedded in a ceramic matrix. In gas turbine engines and the like, example fibers of interest include silicon carbide or carbon fibers, and example matrices of interest may be silicon carbide or silicon nitride. Such ceramic matrix composites exhibit good strength and chemical properties. At high temperatures the composite can form a protective passive oxide layer. The oxide layer may, however, be subject to volatilization at high temperatures in the presence of moisture. An environmental barrier coating may be used to limit moisture exposure.